Behavioral Models of Drug Abuse and Addiction
To understand the relationship between a particular drug-induced molecular change and drug abuse or addiction, we study animals, in which the molecular change is mimicked or blocked, in behavioral models of addictive disorders. Accordingly, our research group maintains a Behavioral Testing Core Facility, which offers a wide battery of behavioral tests in rats and mice. In addition to assessing the general neurological function of the animal, we have tests for the diverse behavioral effects of drugs of abuse, including the more straightforward assays of locomotor activity and sensitization (the latter describes the progressive increase in locomotor activity seen with repeated drug exposures), conditioned place preference (where animals learn to prefer a drug paired environment), and withdrawal syndromes upon cessation of drug treatment. Other models are more com
plex and involve an animal’s operant responding to drugs and other stimuli. Animals self-administer and addict themselves to the same range of drugs that humans self-administer and addict themselves to. After a period of withdrawal, they also relapse to drug self-administration, something which is promoted by stress, drug-associated environmental cues, or the drug itself, just as in human addicts. Animals also work to inject electrical current directly into the brain’s reward regions, which is enhanced by drugs of abuse. These operant tasks are powerful models of drug addiction. Our Behavioral Testing Core Facility also has tests of natural reward (including sexual and feeding behavior), depression- and anxiety-like behavior, and cognitive function. Together, we can formulate highly specific hypotheses concerning how a change in a particular protein within a given brain reward region causes certain aspects of addiction.